The present invention relates to a magnetic recording medium. More particularly, it relates to a coated magnetic recording medium, such as a magnetic recording tape, including a magnetic upper layer coated on to a lower support layer, and methods of manufacturing the same.
Magnetic recording media, such as magnetic recording tapes, have continually evolved to satisfy the seemingly endless need for increased recording density or capacity per unit volume. In general terms, magnetic recording media generally comprise a magnetic layer coated onto at least one side of a non-magnetic substrate (e.g., a film for magnetic recording tape applications). With certain designs, the magnetic coating (or “front coating”) is formed as a single layer. In an effort to reduce a thickness of this magnetic recording layer, a more recent approach is to form the front coating as a dual layer construction, including a support layer (or “lower layer”) on the substrate and a reduced-thickness magnetic layer (or “upper layer”) formed directly on the support or lower layer. With this construction, the lower layer is typically non-magnetic or substantially non-magnetic, generally comprised of a non-magnetic powder and a binder. Conversely, the upper layer comprises a magnetic metal particle powder or pigment dispersed in a polymeric binder. Finally, with magnetic recording tape, a backside coating is applied to the other side of the non-magnetic substrate in order to improve the durability, conductivity, and tracking characteristics of the media.
As might be expected, the formulation intricacies associated with the requisite upper layer, lower layer; and back coat, as well as coating of the same to an appropriate substrate, are highly complex, and vary from manufacturer to manufacturer. That is to say, the numerous chemistry and processing variables magnetic recording media invariably result in each magnetic recording media manufacturer having different layer formulations and processing techniques.
Notwithstanding the inherent component and processing variations, certain base materials are commonly employed with many magnetic recording media, including magnetic recording tapes. To this end, magnetic tapes from two different tape manufacturers will often employ several of the same components in one or more of the upper layer, lower layer and back coat. Thus, any improvements to these common material types, amounts or performance characteristics can be universally beneficial. For example, conductive carbon black is typically used as the lower layer conductivity component. Unfortunately, the amount of conductive carbon black normally required to provide requisite conductivity can negatively affect rheology and dispersion quality of the overall lower layer coating.
The conductive carbon black concern described above is but one example of macro-level issues faced by many magnetic recording media manufactures. With reference to specific magnetic recording tape formats, a multitude of other, more exacting formulation and processing issues must be addressed. Thus, a need exists for a magnetic recording medium that exceeds performance requirements and entails broadly applicable improvements.